Sunday, May 23, 2010

camshaft vs crankshaft

crankshaft: transfer the rotational energy
camshaft: to operate poppet valves

usually overhead camshafts

camshaft + cam <--> valves + cylinder+piston <--> crankshaft

multi-valve > 2 valves.

4 stroke engine

Intake valve: induction
exhaust valve:

1st and 4th strokes need different valves (lets leave aside two stroke engines)

Some have 2 intake valves, 2 exhaust valves or 2+3. SOme make use of dual overhead camshafts to accomodate em.

Timing belt/chain connects camshaft(s) and crankshaft, along with others like water pump.

timing belts/chain transmit torque from the engine crankshaft to the engine camshaft that opens the valves that admit air and fuel.

If timing belt breaks, camshaft stops, but crankshaft continues to run, thereby messing up valves. This is the case with interference engines.

What are int. engines?

A design:

"Valves open further in an interference engine and project further into the combustion chamber than in a 'free-running' engine. This allows outside air at atmospheric pressure flow faster into the combustion chamber through the larger valve opening. The engine can therefore inhale more air, be a little smaller, and still create as much power while reducing its manufactured cost and also guaranteeing future repair business for its dealer"

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